5 Killer Queora Answers On Machine Espresso
How Does Machine Espresso Work?
Machine espresso employs precise pressure and amazing filter technology to make the perfect cup of coffee. What exactly is it that makes it work?
Espresso is created by forcing hot water under high pressure through finely ground coffee. The process is similar to that of making drip coffee. However the pressure is the main difference.
The Group Head
The group head is the portafilter you put in when making espresso. It disperses water in the portafilter, and controls the pressure of the extraction. There are several different types of group heads each with its unique advantages and drawbacks. Some are designed to provide stability in temperature, while others are specifically designed to handle pre-infusion. Others are made to control the lever. Some have a combination of features, such as the E61, which is the classic choice among many baristas due to its ability to provide multiple benefits in a single package.
As you can see from the photo above the head of the group is fitted with a variety of notches. It is possible to place your portafilter in these notches, then twist the head to lock it. A gasket made of rubber is positioned inside the notches to help create a seal as you insert your portafilter. The notches allow for the precise placement of the portafilter. This is crucial to ensure an efficient extraction.
The group head not only allows you to put in your portafilter easily however, it also keeps an even temperature. This is achieved by cycling hot water around the portafilter and through the brew-basket, ensuring that the temperature is constant for extraction. This is important, as even a small difference in temperature can mean the difference between good and excellent espresso.
The Pump
The motorized pumps that are used in espresso machines that rotate provide the nine atmospheric bars of pressure required to extract espresso. This is different from manual piston machines which use a lever. This pressure is built up by pumping water through a heat-exchanger and then through the ground coffee.
Pumps are generally less expensive than piston-driven machines, and they tend to last longer, but both types of machines may become damaged due to excessive use and poor cleaning. Pumps are also more complex mechanically, and can add to the price of even the simplest models.
Some espresso machines employ steam pressure instead of a pump in order to brew espresso. This could lead to over-extraction since the boiler that produces steam also warms the water to boil. The machines also need to continually rebuild their pressure between cups. This takes energy and time.
A large majority of espresso machines employ an rotary or a vibration pump. A vibration model uses a vibrating disk to generate pressure, whereas the rotating model pushes hot water through the ground at high speed. Both types of machine can produce an excellent espresso maker barista, however the rotary pumps are quieter, and more durable than vibration pumps.
The Boiler
The boiler is what will heat the water to the perfect temperature to extract. The resultant steam then reaches the portafilter containing the ground espresso coffee, and is then pumped down into the cup. During this process, the steam creates pressure to push through the coffee grounds. This results in a whipped-up top of the espresso. This is one of the main characteristics of a good espresso.
There are three kinds of espresso makers, and they differ in the kind of pump they use and how hot the espresso is. There are different ways that the brew can be controlled and the size of the cup that the machine can produce.
The earliest espresso machines were steam type. They employed one boiler to create both steam and brew, however the pressure they were able to generate was low - only two bars of atmospheric pressure at most. This resulted in the coffee tasting burnt and bitter. The modern espresso machine was created by the Milanese producers Luigi Bezzerra & Desiderio Pavoni.
The most well-known espresso machine is a semiautomatic that has an electric pump. When people think of espresso machines, they picture these machines espresso. If you have a semi-automatic machine you have to grind the beans and then tamp them yourself but the pump controls the flow of water and pressure. This is a perfect combination of human control and mechanised reliability.
The Filter
espresso machine with milk frother machines typically use a filter that separates the coffee grounds from the hot water. The filter is also an important component of the temperature control system as it prevents the machine from overheating.
It also helps with flavor, since a filter allows for a longer bloom phase. This allows the beans to release their nuances and gives the chance for better extraction.
It is important to remember that even the best cheap espresso machine filter can make a bad cup of coffee. The quality of the beans and the extraction, remain vital.
This is where the magic happens. It's what makes espresso taste great. The grouphead (also called the brewhead) is where you put the portafilter, the thingy which you put the grounds of your coffee into when making espresso.
In a steam-driven espresso machine, hot water is heated in an airtight tank to create steam. This then pushes the hot water through the grounds under high pressure. These types of machines are usually less expensive and easier to maintain than pump-driven models. They are however limited to create the perfect conditions for brewing since they only operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars.
In recent years, compressed air-driven espresso machines have become more popular. They utilize an air compressor to push hot water through grounds and are much more portable than steam-driven electric machines.
